Don't leave the apt or do ANYTHING without the advice of an attorney. Contact the local legal aid office (check the phone book). There are TONS of organizations at the local level willing to help battered women. He has no right to withhold your money and he should be ordered to pay it back to you.
He can't throw you out without evicting you. He can call he cops...do whatever, but they will also not make you leave. This is a civil matter. Unless, of course there is violance and if he hits you, call the police yourself. They will remove him, not you! Don't put your hands on him and protect your child.
Have you considered not giving him your portion of the rent money and deducting it from your portion of the refund you are legally owed? Ask an attorney about this.
You need some legal advice, go hit the yellow pages today.

